Tax Basis of Item Pawned and Redeemed

If you buy a gold watch for 850, pawn for 350, redeem for 350 and 225 in interest, what is your cost basis if the watch is subsequently sold? What if the watch is pawned more than once? Finally, the watch is pawned, lost, and the pawnbroker agrees to sell it back on lay away for the principal plus interest owed? More than one watch is involved.

Tax Basis of Item Pawned and Redeemed